Device for transmitting and receiving compressional waves



June 14, 1949. BENIOFF 2,473,354

DEVICE FOR TRANSMITTING AND RECEIVING COMPRESSIONAL WAVES Original Filed Nov. 20, 1942 4 Sheets-Sheet 1 FIG. I

INVENTOR ATTOR Y June 14, 1949.

H. BENIOFF DEVICE FOR TRANSMITTING AND RECEIVING COMPRESSIONAL WAVES Original Filed Nov. 20.' 1942 4 Sheets-Sheet 2 INVENTOR BY Hucao BENIOFF ATTORIZIQ YZ;

June 14, 1949. BENIOFF 2,473,354

DEVICE FOR NSMI 'r ne AND macmvms COMPRESSI AL WAVES Original Filed Nov. 20, 1942 4 Sheets-Sheet 5 INVENTOR f I Y Hucao BENIOFF I AT E Y June 14, 1949.

4 Sheets-$heet 4 Original Filed Nov. 20, 1942 F F 2 m 4 l I E O o hwy/UTE. a W 6 m Patented June 14, 1949 PATENT, oFFlcE DEVICE FOR TRANSMITTING AND RECEIV- IN G COMPRESSIONAL WAVES Hugo Beniofl, Pasadena. Calif., assignor, by mesne assignments, to Submarine Signal Company, Boston, Mass, a corporation of Delaware Original application November 20, 1942, Serial No.

466,535. Divided and this application January 10, 1948, Serial No. 1,651

6 Claims.

The present application is a division of my application Serial No. 466,535, filed November 20, 1942, now Patent No. 2,450,412, granted Octoher 5, 1948.

The present invention relates to improvements in subaqueous apparatus and finds its chief merits and advantages over the prior art in improvements and construction providing an improved electroacoustic transducer capable of being used under great hydrostatic pressure.

Further merits of the present invention are found in means of acoustically coupling the vibration-transducing means with the water medium. In the present invention the radiating member comprises a plurality of similar longitudinally vibrating passive resonant elements closely spaced one from the other in a symmetrical pattern and joined in a flange embracing a plane in which the nodal points for all the resonant elements lie. is such that the radiation takes place from the outer surface of the longitudinal resonant elements in such a fashion that the amplitude of each element may be independently controlled by the generating means producing the longitug5 dinal resonant vibrations;

A still further object of the present invention is to provide an electroacoustic transducer capable of withstanding not only normally high hydrostatic pressures, but also excessively high impulse pressure such as may be caused by explosions and the like in the medium in the vicinity of the device.

A further advantage in the construction of the present invention is that the entire operating unit comprising the radiating element and .the translating element are all supported by the single nodal plane mounting and that the supwp'orting case carries projecting members in op- :posed relation to the radiating units at many points so that if an excessive shock is received,

as, for instance, by the discharge of the bomb, the radiating member will seat itself against these supporting elements and prevent damage to the translating units.

Fu'rther advantages and merits of the present invention will be more fully explained and understood in connection with the drawings showing tin-embodiment of the same in which Fig. 1 shows a'pl'a'n-view of-an embodiment of the invention:

Fig. 2 shows a section taken on the line 2-2 of Fig. 1; Fig. 3'shows a detailed exploded view of the translating Lnit of Fig. 2 in section; Fig. 4 shows-a section taken on the line 4-4 of Fig. 3

Fig. 5 shows a detail section taken on the line 56 The resulting structure at 5-5 of Fig. 2; Fig. 6 shows a modification of the embodiment of Figs. 1, 2 and 5 using a piezoelectric translating element; Fig. '7 shows a modification of a detail of the present invention; Figs. 8 and 8a show a further modification of a detail of the invention; Figs. 9, 10 and 11 show further modifications of details of the invention; and Fig. 12 is a section taken on the line l2'l2 of Fig. 11 but extendig over a greater fragment than that shown in Fig. 11.

In the arrangement shown in the figures described there is provided a casing I of durable metal as, for instance, steel or other suitable material which is covered by an insulating coating I00 of cork or the like which extends from the edge of the active diaphragm surface all over the back of the casing. The cover plate 2 has a portion serving as a compressional wave radiating element. The cover plate includes a peripheral flange 3 in which the cover is bolted to the casing by means of a group of rim bolts 4. The cover 2 has projecting from one face externally of the casing a plurality of projecting blocks 5. 5 which are indicated in Fig. 1 as squares but which may, of course, be in other forms, as, for instance, hexagonal, octagonal, circular or the like. Similarly, shaped blocks 6, 6, 6, etc. project from the cover within the casing aligned with the blocks 5. These projecting blocks 5 and 6 may be made integral with the cover itself or they may be attached to it by suitable bolts or in other known manners. The blocks 5 and 6 form with the supporting ilange 3 one-half wave length resonant elements and may therefore be used as a resonant coupling element with the water to provide efficient acoustic coupling between the translating elementand the water. These may be called passlve vibrators as they are coupling units between the medium and the active vibrating elements. If the projecting blocks 5 and 6 are substantially of the same construction, then the unit provides at both faces substantially the same vibrational amplitude, while if one is longer than the other, the end face of the longer unit will have the greater amplitude. For a 20 kilocycle projector these blocks, if made of steel, may have surface dimensions approximately one and one-half the magnetostrictive element 1 and being screwed into the face of the block 5.

The active magnetostrictive element is made of nickel or some suitable metal and comprises the base section In of substantial mass and rigidity which may be circular in section. The magnetostrictive element 1 has formed on the base In a section having a conical surface Ii which is integral at its end with a cylindrical element i2. The thin cylindrical element l2 supports at its end a cylindrical mass member l3, the support being at the center of percussion of the cylinder l3 which is at a point more than half way out on the section i3, as indicated in Fig. 3. The magnetostrictive element I, in effect, therefore, comprises a short cylindrical member to which is joined at each end mass members whose ratio is chosen according to the amplitude transformation desired. Since it is attached to the passive vibrator at an antinode. this permits a freedom of choice of mass ratios with their corresponding transformation ratios not possible in other structures. The cylindrical members are hollowed to receive the magnetic polarizing member l4 which may be a magnet of Alnico or some such similar material capable of retaining a large permanent magnetizing effect. The permanent magnet l4 may be a solid cylindrical element fitting concentrically within the cylinders l2 and i3 and supported in a holder l5 which is recessed in its front face at Hi to receive by forced fit the end of the magnet l4. The holder I5 is retained in the support I! by means of the machine screw 18 in the recess l9 and this supporting member, in turn, is seated in the recess 2| of the plate 20 and is held to the plate 20 by the screws 22 which pass through the flange 23 of the member I1 into the plate 20.

The magnetostrictive element 1 has an energizing coil 24 which may also serve to carry a polarizing current and which is wound on a split form 25 after the form has been placed over the magnetostrictive member. The coil 24 may have any desired impedance in accordance with a choice of suitable electrical constants and this coil is located in a recess in the form '25 directly adjacent to the cylindrical stem I2. The coil form 25 fits around the cylinder l3 but is spaced away from it so that vibration of the magnetostrictive element does not bring it into contact with the coil form in any way. The coil form 25 is also supported from the plate 20 by means of the screws 26 which pass through the plate 20 and thread into the end faces of the coil forms 25.

The plate 20 which holds the polarizing magnet l4 and the coil form 25 of each of the magnetostrictive units 1 is supported around its periphery by a group of rods 21, which rods are threaded into the plate 3. The coils 24 may be connected together in any desired series or seriesparallel arrangement and are energized through the cables 28 and 29 which pass through the stuffing gland 30 mounted on a projecting flange 3| projecting from the rear of the casing.

When the magnetostrictive element is rigidly fastened to the block 6 by means of the conicalheaded screw 8 in the conical cavity 32 at the center of the base of the magnetostrictive member, the magnetostrictive element becomes a standing wave member at the operating resonant frequency at which the oscillator or projector is designed to operate. The desired ratio of transformation is established by properly proportioning the masses of the base In of the magnetostrictive unit and the end cylinder l3. The radiating or cover member 2 with the projecting blocks 5 and 6 on opposite sides of it are also established as one-half wave length element with the central flange 3 embracing the node of this element as a vibrator. This central flange 3 may be made heavy enough to withstand the pressure encountered in mounting the unit on the ocean floor in places where it is desired to be used. Also, as has been explained, the reaction of the flange element increases slightly the effective elastic modulus of the central section of the longitudinal element and raises the vibrational frequency as compared to a similar unrestrained vibrator.

Mounted Within the casing l on the back wall 33 are a group of studs or rods 34 which project upwards through the plate 20 and have their end surfaces opposed to the corners of each of the blocks 6. As indicated in Fig. 5, the base H) of the magnetostrictive units being circular provides sufficient opening over the corners on the face of the block 6 so that the rods 34 have sufficient room to extend upwards from the base 33. The clearance between the face of the rods 36 and that of the block 6 may be just a little more than the normal working maximum amplitude of motion for the block 6 so that, when an explosion or excessive vibration occurs, an added support will be furnished to the cover 2 at a reat number of points over its whole area and thereby help the unit to withstand considerably more pressure than that normally needed to be withstood for the depth of submergence.

The blocks 5 and 6 on either side of the cover may be arranged, as indicated in Fig. 1, to cover substantially the whole surface. The grooves 35 between adjacent blocks 5 may be made any desired width. Where the blocks are made separately and attached to the diaphragm, the units can be placed as close as desired providing the sidewise expansion of the blocks does not interfere with the longitudinal vibrations.

The grooves between the radiating elements are shown small compared to the dimensions of the elements. Under conditions where the driving elements operate better with relatively larger amplitudes, the grooves may be made larger.

In the arrangement shown in Fig. 6, the cover unit 40 is similar to that described in Figs. 1 to 5 and is mounted in a casing l which has studs 34 projecting from the rear thereof. The cover unit 40 is provided with projecting blocks 4| and 42, the latter carrying piezoelectric vibratory elements 43, such as Rochelle-salt, quartz, etc., with electrodes 44, 44, 44, attached to the side faces of the crystals. These crystals may be cemented directly or in grooves 45 on the end faces of the block 42, adjacent crystals being separated and spaced by projecting ribs 46 forming the sides of the grooves. The crystals are mounted in groups or individually on the end faces of the block and may have their electrode connections brought out to a terminal 49 on the insulating plate 48 supported by the rods 21' from the cover 40. The plate 48 has perforations 50 to permit the plate to fit over the studs. These crystals 43 have substantially the same frequency when vibrating as half wave length vibrators as the resonant structure formed by opposing blocks 4| and 42 and the central portion of the cover 40.

The crystals may be mounted within the easing in an air or gas medium or they may be mounted on the outside face of the casing, in which case the casing should preferably be cova- 'rasse ered' over or immersed in an oil medium. For

this purpose a housing may be placed over the front of the casing and this maintained'fllled with castor oil or other suitable acoustic medium in which the crystals will not be harmed.

In Fig. 7 a further modification of the arrangement of the magnetostrictive unit illustrated in Figs. 2 and 4 is shown; Here the block member 5|, corresponding-to the block 8, has mounted on it a magnetostrictive member 52 which is pro-- 'vided with a heavy base 53topped by a conical member 54 merging into a cylindrical tube portion 55 which is free at the end. The magnetostrictive unit 531s firmly secured to the block 5| by means of the screw 56 which rests in a conical cavity 51 in the base and firmly holds the magnetostrictiveunit 52 to the block. The mag-netostrictive element is polarized by means of the permanent magnet 58 which is cylindrical in form and has at its lower end a head 58 forming a pole-piece, which fits into the conical cavity 5'! of the mag- .netostrictive element. The magnet 58 also at .its top end has a flat pole piece 68 which may be fitted over the end of the magnet. The flat surface of the magnet is positioned over the end of the magnetostrictive member '55 and completes the magnetic path through the magnetostrictive cylindrical portion. The energizing of the magnetostrictive element is supplied by the coil 6| which may be wound on a forxn;82 supported directly by the plate 63 corresponding to-the plate 28 of Fig. 2. The magnets and their pole pieces or some similar synthetic composition as far as its I I acoustic properties are concerned. The passive Y may also similarly be supported by the plate 63 so that both these units are simultaneously removable when the plate 63 is removed. The use of the straight cylindrical magnetostrictive ele ment 55 permits a non-split coil form to be used and the coil to be wound before it is put over the magnetostrictive unit. v

In the use of the unit of the type shown in Fig. 7 for'mounting on the back of the blocks of the oscillator, the distribution of the mass with a heavy mass 53 at the base of the unit is such as I to bring the node, when the unit is used as a half wave length element, in the vicinity of the base and permit, relative to the radiating surface amplitudes, large amplitudes of the magnetostrictive member, particularly near its free end.

The apparatus described in the present speciflcation hasparticular utility in the production of a beam of supersonic compressional waves. In this connection the energy applied to each unit in the structure may be such as to obtain the U desired beam pattern both in relation to the angular opening of the beam and the control of secondary lobes around the central. main beam. By' properly choosing and increasing the energy of the central blocks over those around the periphery, secondary lobes may be substantially reduced. This is easily obtained either by prop-- moving coil type, electromagnetic of the variable erly proportioning the windings or supplying otherwise the desired amounts of energy to each unit. The device in any of the forms described may be used in deep water, as, for instance, on a tripod mounting and will withstand, because'of the heavy central flange, a substantial water pressure and yet provide free piston action be,- cause of the location of the mounting flange with respect tothe radiating surface. Due to the reaction of the thick central fiang the central blocks or vibrating 'units for the same length havea higher natural frequency than,

those blocks at the edges so that these blocks nearer the "center for the same tuning are slightly longer than those at the edges. 3

In the arrangements described in Figs. 1 tot. the translating elements or the vibrating amt; were positioned within the casing protected'from the water medium. In the arrangement of Fig. '8

the translating elements may also be placed on" the radiating side of the radiating unit andacoustically coupled with the sound-propagating medium by means of some suitable liquid, plastic or other In the. arrangement shown in Fig. 8 the diaphragm element Ill is within a dome 14 havingliquid, which dome-is sound-conductive material.

formed by the shell II of a material to permit passage of compressional vibrations with-:little 1 interference or attenuation. The'diaphrag'mcar ries a plurality of longitudinal vibratingelements '12 on both its rates. On the ends of the vibrating elements in contact with the propagating me dium are grooves in which arexmounted a group of piezoelectric vibrators l3, l3, I3. 13. This con-'- struction may be similar to that shown in Fig. ,6

with the exception that the units 13, 13, 13,13, ,etc., are mounted on the front of the casing within the liquid-filled dome which may be of rubber vibrating elements I2 within the casing away from contact with the propagating medium may"! carry magnetostrictive units 81 or other active vibratory elements.

In the arrangement of Fig. 8 the longitudinal vibrator, made up .of the whole vibrating elementincluding both blocks 12 on both sides of the cover itself, and the vibrating unit 13 combine to form together one wave length or an'integral number. of half wave lengths addedto this at the free quency at which the supersonic waves are to *be propagated and received. The blocks 12 andwith I the cover portion in between form a one-half wave length element, and the unit 13 forms the other half-wave length element.

such as air. While in the description of "Fig. "8

the vibrating units 13 are described as piezo electric elements, which may be Rochelle-salt crystals or any other type of piezoelectric vibrat ing elements, nevertheless, electrodynamic of the reluctance type, or magnetostriction vibrating units, as illustrated in Fig. 8a where the magnetostrictive hollow-cylindrically shaped units 13 are mounted on the blocks 12, may also be used in place of the elements 13 as described inconnection with the other figures of the specification. In Fig. 8a a permanent magnet l4 may serve to provide the constant flux excitation by its poles adjacent the inner walls of the magneto strictive cylindrical elements.

In Figs. 9 and 10 a cover plate 88 of uniform thickness is used on which are mounted members to form resonant structures vibrating at right 8 angles to the cover plate. In Fig. 9' the blocks on one side of the plate are 8|, 8|, and on the other side of the plate 82, 82. These blocksare held to the cover. plate respectively by screws 83,

83 and 84, 84 positioned centrally in the blocks.

In Fig. 10 the resonant structure is formed by longitudinal elements 85, 85 and 86, 86 which may be made heavier at their free end surfaces, ifdev sired, thereby loading the elements in accordance with the design of the structure as chosen. In,

both Figs. 9 and 10 the top holes in the elements... 8| and 85 may be filled at their ends by plugs 81', 81' to. form a continuous surface of that por I In this ar a rangement it should also be noted that the space 10' within the casing 18- is filled with amedium having a comparatively low radiation resistance tion of the elements exposed to the acoustic propagating medium.

In both Figs. 9 and 10 the elements 82 and 86 respectively have attached at their ends the half wave length transducing elements '81 and 88 respectively which in these figures are shown as magnetostrictive elements similar to the element 1 of Fig. 2.

In Figs. 11 and 12 the magnetostrictive unit 1 is shown attached by screws 9| to a comparatively thin diaphragm 90. Here the unit I with the diaphragm portion adjoining it may :make up a half wave length element. The units 1 are preferably nested together on the diaphragm as shown in Fig. 12, but a single element may alone be used in a transmitter or receiver. The construction of the unit I of Fig. 11 is otherwise similar to that illustrated in Fig. 2 and the same numerals have been applied to similar parts.

Having now described my invention, I claim:

1. A device for transmitting and receiving compressional wave energy comprising a casing having a radiating memberat .one side thereof with the external surface in acoustic relationship with a sound-propagating medium and the interior surface shielded therefrom, said member having passive vibrating elements aligned at right angles to said member, and active resonant vibratory elements mounted at both ends of said passive vibrators.

2. A device for transmitting and receiving compressional wave energy comprising a casing having a radiating member at one side thereof with the external surface in acoustic relationship with a sound-propagating medium and the interior surface shielded therefrom, said member having passive vibrating elements aligned at right angles to said member, and active resonant vibratory elements mounted at the ends of said passive vibrators, one group of said active resonant vibrators on one side of said radiating member being piezoelectric elements and the group on the other side of said radiating member being magnetostrictive elements.

3. A device for transmitting and receivingv compressional wave energy comprising a casing having a radiating member at one side thereof with the external surface in acoustic relationship with a sound-propagating medium and the interior surface shielded therefrom, said member having passive vibrating elements aligned at right angles to said member, and active resonant vibratory elements mounted at the ends of said passive vibrators, one group of said active resonant vibrators on'one side of said radiating member being piezoelectric elements and the group on the other side of said radiating member being ma netostrictive elements, and a shell formed on the outside of said casing surrounding the external surface of the radiating member and the active elements thereon, said shell being in acoustic contact with the wave propagating medium, and means filling the space within the shell providing an acoustic coupling between the active units outside of the cover, a shell formed on the outside of said casing in acoustic contact with the water and means filling the space within the shell providing an acoustic coupling between the longitudinal units therein and the external water medium.

5. In a device for transmitting and receiving compressional waves comprising a casing having a heavy cover member secured at its edge to said casing and completely'enclosing the same. said cover having projecting members extending therefrom on either side thereof forming longitudinal vibrators in which the cover forms a central heavy section embracing the nodal plane,-

resonant vibrating translating units mounted at the end of said longitudinal vibrating elements on the outside of the cover, a shell formed on the outside of said casing in acoustic contact with the water and means filling the space within the shell providing an acoustic coupling between the longitudinal units therein and the external water medium, said translating units comprising resonant longitudinal vibrating magnetostrictive elements having permanent magnet excitation.

6. In a device for transmitting and receiving compressional waves comprising a casing having a heavy cover member secured at its edge to said casing and completely enclosing the same, said cover having projecting members extending therefrom on either side thereof forming longitudinal vibrators in which the cover forms a central heavy section embracing the nodal plane, resonant vibrating translating units mounted at the end of said longitudinal vibrating elements on the outside of the cover, a shell formed on the outside of said casing in acoustic contact with the water and means filling the space within the shell providing an acoustic coupling between-the REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,233,992 Wyckoff Mar. 4, 1941 2,405,226 Mason Aug. 6,1946 I having projecting members extending 

